1. Technical Field
The present invention relates to a piezoelectric oscillator, a GPS receiver device, and an electronic apparatus.
2. Related Art
As a positioning system using satellites, a GPS (Global Positioning System) is widely known and is used in car navigation devices and the like. The GPS receives electric wave signals in the 1.5 GHz band, which are transmitted from a plurality of GPS satellites orbiting the Earth, by using a GPS receiver device and performs a process (position calculation process) of calculating the current position based on orbit information and time information that are superimposed in the received electric wave signals and a time correcting process.
The GPS receiver device performs RF signal processing in which GPS electric waves are received and are converted into a signal in the intermediate frequency band and baseband signal processing in which a baseband signal is demodulated from the signal in the intermediate frequency band, and position calculation and the like are performed based on the baseband signal. The baseband signal processing can be performed with a clock signal with frequency accuracy having a frequency error of about ±100 ppm without any problem. However, in order to be precisely locked to a GPS electric wave signal, the RF signal processing needs a clock signal with extremely high frequency accuracy having a frequency error within ±0.5 ppm. Accordingly, a temperature compensated x'tal oscillator (TCXO) from which a clock signal with high frequency accuracy can be acquired is widely used. The temperature-compensated crystal oscillator (TCXO) outputs a clock signal having an almost constant frequency regardless of the temperature by cancelling a deviation (frequency variations) of the oscillation frequency of a quartz crystal resonator from a desired frequency (nominal frequency) within a predetermined temperature range.
JP-A-2003-163542 is an example of related art.
Recently, the GPS receiver device is built in not only an installation-type electronic apparatus such as a car navigation device but also a portable electronic apparatus such as a cellular phone or a wrist watch. Thus, there is a demand for low power consumption of the GPS receiver device. Furthermore, the power consumption of a circuit that performs the RF signal processing or the baseband signal processing is reduced to a large extent in accordance with advances in technology. As a result, the ratio of the power consumption of the temperature-compensated crystal oscillator (TCXO) to the power consumption of the entire GPS receiver device significantly increases. Therefore, it is important to reduce the power consumption of the temperature-compensated crystal oscillator (TCXO) in a GPS receiver device that is built in a portable electronic apparatus.